Underfilled semiconductor die assemblies and methods of forming the same

ABSTRACT

An apparatus and method for packaging a semiconductor die and a carrier substrate to substantially prevent trapped moisture therebetween and provide a robust, inflexible cost-effective bond. The semiconductor die is attached to the carrier substrate with a plurality of discrete adhesive elements so as to provide a gap or standoff therebetween. Wire bonds may then be formed between bond pads on the semiconductor die to conductive pads or terminals on the carrier substrate. With this arrangement, a dielectric filler material is disposed in the gap or standoff to form a permanent bonding agent between the semiconductor die and the carrier substrate. By applying the dielectric filler material after forming the wire bonds, the dielectric filler material coats at least a portion of the wire bonds to stabilize the wire bonds and prevent wire sweep in an encapsulation process, such as transfer molding, performed thereafter.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 10/191,655,filed Jul. 8, 2002, pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to methods and apparatus forassembling semiconductor dice to a carrier substrate. In particular, thepresent invention relates to methods and apparatus of underfill bondingsemiconductor dice to a carrier substrate and various assemblyarrangements with respect to underfill bonding semiconductor dice to acarrier substrate followed by encapsulation.

2. State of the Art

Chip-On-Board (“COB”) or Board-On-Chip (“BOC”) technology is used toattach a semiconductor die directly to a carrier substrate, such as aninterposer or printed circuit board. Electrical and mechanicalinterconnection used in COB or BOC technology may include flip-chipattachment techniques, wire bonding techniques, or tape automatedbonding (“TAB”) techniques.

Flip-chip attachment generally includes electrically and mechanicallyattaching a semiconductor die by its active surface to a carriersubstrate using a pattern of discrete conductive elements therebetween.The discrete conductive elements are generally disposed on the activesurface of the die or an interposer during fabrication of thesemiconductor die package, but may instead be disposed on the carriersubstrate. The discrete conductive elements may comprise minuteconductive bumps, balls or columns of various configurations. Eachdiscrete conductive element is placed corresponding to mutually alignedlocations of bond pads (or other I/O locations) on the semiconductor die(or interposer) and terminals on the carrier substrate when the twocomponents are superimposed. The semiconductor die is thus electricallyand mechanically connected to the carrier substrate by, for example,reflowing conductive bumps of solder or curing conductive orconductor-filled epoxy bumps. A dielectric underfill may then bedisposed between the die and the carrier substrate and around thediscrete conductive elements for environmental protection and to enhancethe mechanical attachment of the die to the carrier substrate. Forexample, U.S. Pat. No. 5,710,071 to Beddingfield et al. discloses anexemplary flip-chip attachment of a semiconductor die to a substrate anda method of underfilling a gap between the semiconductor die andsubstrate.

Wire bonding and TAB attachment techniques generally begin withattaching a semiconductor die by its back side or its active surface tothe surface of a carrier substrate with an appropriate adhesive, such asan epoxy or silver solder, a liquid or gel adhesive, a double-sidedadhesive-coated tape segment such as Kapton®, a polyimide. In wirebonding, fine wires of gold, aluminum or alloys thereof, are discretelyattached to bond pads on the semiconductor die and then extended andbonded to corresponding terminal pads on the carrier substrate. Adielectric encapsulant such as a silicone or epoxy may then be appliedto protect the fine wires and bond sites. In TAB attachment, ends ofmetal traces carried on a flexible insulating tape such as a polyimideare attached, as by thermocompression bonding, directly to the bond padson the semiconductor die and corresponding terminal pads on the carriersubstrate.

Particularly in the case of wire bonding followed by transfer or othermolding process to encapsulate a die and carrier substrate assembly,there are problems in securing the semiconductor dice to the carriersubstrates using an adhesive-coated tape. Specifically, byconventionally utilizing adhesive tape in attaching a semiconductor dieto a carrier substrate followed by overmolding, moisture associated withthe adhesive becomes trapped, ultimately resulting in moisturesensitivity issues in the form of enhanced potential for delamination ofthe components of the semiconductor die assembly. Further, the cost ofthe large volume of adhesive tape used to attach large numbers of diceto carrier substrates becomes excessive. In addition, the conventionaluse of substantial volumes (as measured by surface area) of tape isrequired to avoid stress defect failure in semiconductor die assemblies.Finally, even with the use of substantial tape coverage between asemiconductor die and its carrier substrate, the bond and resultingassembly may be undesirably flexible and resilient.

Another ongoing problem with the use of wire bonding in packaging occursduring a transfer molding encapsulation process of the semiconductor diein what is known as “wire sweep”. Wire sweep results when a wave frontof dielectric (commonly a silicon-filled polymer) encapsulation materialmoving through a mold cavity across the semiconductor die and carriersubstrate assembly forces wire bonds to contact adjacent wire bonds andbecome fixedly molded in such a contacted position after theencapsulation material sets. When wire sweep occurs, a wire bondinterconnection of a semiconductor die to a carrier substrate shortcircuits, which results in a nonfunctional semiconductor die assembly.Wire bond sweeping may also result in bond wire breakage ordisconnection from a bond pad or terminal.

Yet another problem with conventional techniques is that of bleed ofmolding compound introduced into a mold cavity to form a dielectricencapsulant over the die and carrier substrate, which problemparticularly manifests itself in the case of BOC-type assemblies whereinbond pads of a semiconductor die accessed through a slot in a carriersubstrate are wire bonded prior to encapsulation. Under certainconditions, such as where the die fails to overlap the slotsufficiently, pressure of the molding compound in conjunction with theconfiguration of the assembly causes molding compound to bleed out ofthe mold cavity.

Therefore, it would be advantageous to utilize wire bonding in packagingin combination with an assembly and encapsulation technique tosubstantially eliminate moisture sensitivity issues as well as beingcost efficient and providing a more robust semiconductor die assembly.It would also be advantageous to utilize wire bonding packagingtechniques while substantially eliminating the problem of wire sweep andmolding compound bleed.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to methods and apparatus for mutuallysecuring and encapsulating a semiconductor substrate and a carriersubstrate to substantially reduce or even prevent trapping of moistureat the interface between the semiconductor substrate and carriersubstrate. The present invention also relates to methods and apparatusfor substantially preventing “wire sweep” in wire bonding packagingtechniques.

The semiconductor substrate includes a back surface and an activesurface with bond pads exposed thereon. The carrier substrate includes asurface with conductive pads or terminals exposed thereon. Thesemiconductor substrate is attached to the carrier substrate in aposition and orientation so that wire bonds may be extended between theconductive pads or terminals on the surface of the carrier substrate andthe bond pads on the active surface of the semiconductor substrate. Suchattachment is facilitated by a plurality of adhesive elements ofrelatively small surface area, in comparison to the “footprint” of thesemiconductor substrate over the carrier substrate, which provides aninitial bond between the semiconductor substrate and the carriersubstrate while providing a gap or standoff therebetween. A dielectricfiller material is then disposed in the gap or standoff area to act as apermanent bonding agent between the semiconductor substrate and thecarrier substrate.

In one embodiment, the carrier substrate includes an opening, forexample, in the form of a slot extending between the first and secondsurface thereof. The semiconductor substrate is attached by its activesurface to a surface of the carrier substrate so that the bond pads ofthe semiconductor substrate are exposed through the opening. Wire bondsare then formed between the exposed bond pads on the semiconductorsubstrate and the conductive pads on the surface of the carriersubstrate opposite that to which the semiconductor substrate is securedso that the wire bonds extend through the opening.

In this embodiment, the dielectric filler material is introduced intothe gap or standoff area between the semiconductor substrate and thecarrier substrate to establish a permanent bond between thesemiconductor substrate and the carrier substrate and to substantiallyfill the slot and secure the wire bond in place. In one aspect of thepresent invention, the dielectric filler material may be applied to thegap or standoff area through the opening in the carrier substrate. Assuch, at least a portion of each of the wire bonds in the opening isencapsulated by the dielectric filler material, stabilizing the wirebonds against potential wire sweep. After applying the dielectric fillermaterial, a dielectric encapsulation material may be applied, as bytransfer molding, injection molding or other technique known in the art,to fully encapsulate the wire bonds, and an overmold of encapsulationmaterial may be likewise applied over the semiconductor substrate on theother side of the carrier substrate.

According to the present invention, the stabilization of the wire bondsvia the dielectric filler material surrounding the wire bonds preventswire sweep between adjacent wire bonds during the encapsulation process.Further, by utilizing the dielectric filler material and not a largeadhesive tape segment or segments to permanently bond the semiconductorsubstrate to the carrier substrate, any moisture sensitivity problems inthe assembled semiconductor die assembly are substantially eliminatedwhile a more robust and rigid bond between the semiconductor substrateand the carrier substrate minimizes the potential for stress defectfailure.

In another embodiment of the present invention, the semiconductorsubstrate may be attached by its back side to the carrier substrate. Insuch an arrangement, the bond pads on the active surface of thesemiconductor substrate are usually proximate one or more peripheraledges thereof. Wire bonds may be formed between the bond pads on thesemiconductor substrate and conductive pads or terminals on the carriersubstrate. Dielectric filler material may be dispensed in the gap orstandoff area provided by a plurality of relatively small surface areaadhesive elements between the semiconductor substrate and carriersubstrate to act as a primary bonding structure between thesemiconductor substrate and carrier substrate. The wire bonds may thenbe encapsulated with an overmolded encapsulation material. Similar tothe first embodiment, bonding the semiconductor substrate to the carriersubstrate using the dielectric filler material substantially preventsmoisture therebetween. The dielectric filler material also surroundsportions of the wire bonds, which stabilizes the wire bonds against wiresweep during the encapsulation process.

In another aspect of the present invention, the semiconductor substrateis mounted to a circuit board in an electronic system, such as acomputer system. In the electronic system, the circuit board iselectrically connected to a processor device which electricallycommunicates with an input device and an output device.

Other features and advantages of the present invention will becomeapparent to those of skill in the art through a consideration of theensuing description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming that which is regarded as the present invention,the advantages of this invention may be ascertained from the followingdescription of the invention when read in conjunction with theaccompanying drawings, wherein:

FIG. 1 illustrates a simplified cross-sectional view of a semiconductorassembly, depicting a semiconductor die attached to a semiconductorsubstrate with an adhesive element providing a gap therebetween,according to a first embodiment of the present invention;

FIG. 2 illustrates a simplified cross-sectional view of a semiconductorassembly, depicting filler material provided in the gap between asemiconductor die and substrate through an opening in the substrate,according to the first embodiment of the present invention;

FIG. 3 illustrates a simplified cross-sectional view of a semiconductorassembly, depicting wire bonds extending through the openingencapsulated by an encapsulation material, according to the firstembodiment of the present invention;

FIG. 4 is a top view of a substrate with an adhesive elementarrangement, according to the first embodiment of the present invention;

FIG. 5 is a top view of a substrate with an adhesive elementarrangement, according to a first variant of the first embodiment of thepresent invention;

FIG. 6 is a top view of a substrate with an adhesive elementarrangement, according to a second variant of the first embodiment ofthe present invention;

FIG. 7 is a top view of a substrate with an adhesive elementarrangement, according to a third variant of the first embodiment of thepresent invention;

FIG. 8 illustrates a simplified cross-sectional view of a semiconductorassembly, depicting a semiconductor die attached face up to asemiconductor substrate with an adhesive element providing a gaptherebetween, according to a second embodiment of the present invention;

FIG. 9 illustrates a simplified cross-sectional view of a semiconductorassembly, depicting filler material provided in the gap between thesemiconductor die and substrate, according to the second embodiment ofthe present invention;

FIG. 10 illustrates a simplified cross-sectional view of a semiconductorassembly, depicting an active surface of the semiconductor dieencapsulated by an encapsulation material, according to the secondembodiment of the present invention; and

FIG. 11 illustrates a block diagram of the semiconductor assembly of thepresent invention interconnected to an electronic system, according tothe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be hereinafter described withreference to the accompanying drawings. It would be understood thatthese illustrations are not to be taken as actual views of any specificapparatus or method of the present invention, but are merely exemplary,idealized representations employed to more clearly and fully depict thepresent invention than might otherwise be possible. Additionally,elements and features common between the drawing figures are designatedby the same or similar reference numerals.

FIGS. 1-3 illustrate a process that may be used for packaging asemiconductor assembly 100. Referring first to FIG. 1, a carriersubstrate 110 is attached to a semiconductor substrate in the form ofsemiconductor die 120 with a plurality of discrete adhesive elements 130therebetween. The carrier substrate 110 includes a first surface 112 anda second surface 114, wherein the substrate 110 may include an opening116 therein in, for example, the form of a slot extending from the firstsurface 112 to the second surface 114. The carrier substrate 110 may beany suitable type of substrate known in the art, such as an interposeror printed circuit board. Carrier substrate 110 may also be made of anytype of substrate material known in the art, such as bismaleimidetriazine (BT) resin, ceramics, or FR-4 or FR-5 materials.

The semiconductor die 120 includes an active surface 122 and a backsurface 124 with bond pads 126 formed on the active surface 122. Thebond pads 126 may be centrally located and exposed in one or more rowson the active surface 122 of the semiconductor die 120 andinterconnected with integrated circuitry (not shown) within thesemiconductor die 120. The semiconductor die 120 is preferably formedfrom silicon, but may be formed from germanium, gallium arsenide orindium phosphide, or any other known semiconductive material whoseelectrical conductivity and resistivity lie between those of a conductorand an insulator. As used herein, the term “semiconductor substrate”includes singulated dice, groups of dice (partial wafers) and bulksubstrates of semiconductive materials other than conventional wafersand including, without limitation, silicon on glass (SOG), silicon oninsulator (SOI) and silicon on sapphire (SOS) substrates.

The active surface 122 of the semiconductor die 120 is attached facedown (as depicted) to the first surface 112 of the carrier substrate 110so that the bond pads 126 are exposed through the opening 116. Thesemiconductor die 120 is attached to the carrier substrate 110 with oneor more, and preferably at least two, discrete adhesive elements 130.The discrete adhesive elements 130 are configured so as to provide a gapor standoff 132 between the semiconductor die 120 and carrier substrate110. Further, the attachment using one or more discrete adhesiveelements 130 disposed between the semiconductor die 120 and the carriersubstrate 110 is sized and configured as a temporary attachment tosecure the semiconductor die 120 and carrier substrate 110 together inproper relative position and alignment prior to the introduction ofanother, primary bonding agent between the two components. The adhesiveelements 130 may be any known adhesive structures, such asadhesive-coated dielectric tape segments such as Kapton® or otherpolymer segments, reduced tape decals, or epoxy drops applied to one ofthe components and partially cured before application of the otherthereto, preformed adhesive segments, or the like. The adhesive elements130 may also comprise metallic or other conductive bonding elements,such as a bond facilitated with solder or solder balls or the like so asto raise the semiconductor die 120 from the surface of the substrate 110to provide the gap or standoff 132 therebetween. Of course, in thatinstance, a suitable dielectric may be interposed between active surface122 and the metallic bonding elements unless the metallic or otherconductive bonding elements were used to ground or electrically bias thesemiconductor die 120. With this arrangement, wire bonds 128 may beformed between the bond pads 126 on the active surface 122 of thesemiconductor die 120 and conductive pads or terminals 118 on the secondsurface 114 of the substrate 110 so that the wire bonds 128 extendthrough the opening 116.

Turning to FIG. 2, the semiconductor assembly 100 is then ready toreceive a dielectric filler material 140 from, for example, a dispenserhead 142. In particular, dielectric filler material 140 may be dispensedfrom the dispenser head 142 so that the dielectric filler material 140is provided to the gap 132 between the semiconductor die 120 and carriersubstrate 110 through the opening 116. The dielectric filler material140 may then extend into and substantially fill the gap 132 by capillaryaction or any other suitable method known in the art, such as methodsutilizing gravity and/or pressurization or application of a vacuum to anouter periphery of gap 132. FIG. 2 is reversed from a conventionalorientation wherein dispenser head 142 is located above thesemiconductor assembly 100 for consistency and clarity among FIGS. 1-3.

According to the present invention, the dielectric filler material 140coats and/or encapsulates at least a portion of the wire bonds 128proximate the bond pads 126 on the active surface 122 of thesemiconductor die 120 and within opening 116. The curing or hardening ofdielectric filler material 140 surrounding the wire bonds 128 provides astabilizing effect to the wire bonds 128 to help prevent movementthereof and wire sweep between adjacent wire bonds 128. Moreover,according to the present invention, by limiting the initial use ofadhesive material as much as possible so as to utilize only the minimumsize, number and arrangement of discrete adhesive elements 130 necessaryto secure semiconductor die 120 to carrier substrate 110 for wirebonding and to provide the gap or standoff 132, any moisture in theadhesive element 130 is also limited. The dielectric filler material 140may then be introduced to fill the gap or standoff 132 and provide apermanent, secure and inflexible bond between the semiconductor die 120and carrier substrate 110, wherein any problems due to moisture beingtrapped therebetween are substantially eliminated. Exemplary, suitablefiller materials T693-R3001EX-V3 and T693-R3002EX-V3, both offered byNagase Chemtex. Also, utilizing dielectric filler material 140 to bondthe semiconductor die 120 to the carrier substrate 110 is much more costeffective, in comparison to utilizing adhesive element or elements as aprimary bonding agent. It should be noted that the particle size of thedielectric filler material is generally substantially smaller thanparticle size of filled polymer encapsulants used, for example, intransfer molding, enhancing flow of the dielectric filler material pastand surrounding wire bonds 128.

FIG. 3 illustrates the semiconductor assembly with an envelope ofdielectric encapsulation material 150 formed thereon. Specifically, adielectric encapsulation material 150 is formed at least partially overthe second surface 114 of the carrier substrate 110 so that each of thewire bonds 128 are fully encapsulated. Dielectric encapsulation material150 may also be formed over the back surface 124 and sides ofsemiconductor die 120, as shown in broken lines. Such dielectricencapsulation material 150 may be provided by transfer molding,injection molding, pot molding or any other suitable technique forencapsulating components of the semiconductor assembly 100. It will,therefore, be well appreciated by one of ordinary skill in the art thatthe dielectric encapsulation material 150 may be formed, for example,using transfer molding over the wire bonds 128 without a wave front ofmolten dielectric encapsulation material 150 causing wire sweep or wirecontact between adjacent wire bonds 128 due to the prior stabilizationof such wire bonds 128 in the coating and/or encapsulating of at least aportion thereof by dielectric filler material 140.

As shown in FIG. 3, semiconductor assembly 100 may be completed in aflip-chip configuration with solder balls, conductive orconductor-filled epoxy bumps, pillars or columns or other discreteconductive elements 160 formed on the second surface 114 of carriersubstrate 110 and electrically connected to conductive pads or terminals118 by conductive traces (not shown), as well known in the art.

FIGS. 4-7 illustrate the carrier substrate 110 with various exemplary,suitable adhesive element arrangements, among a wide variety of adhesiveelement arrangements, that may be utilized for attaching thesemiconductor die 120 thereto. The adhesive element thickness and itsarrangement may be selected to provide an adequate gap or standoff 132to receive dielectric filler material between semiconductor die 120 andcarrier substrate 110 and provide an initial, temporary but adequatelysecure bond between the semiconductor die 120 and carrier substrate 110,after which dielectric filler material 140 may be introduced into thegap or standoff 132 to provide the permanent bond between thesemiconductor die 120 and carrier substrate 110.

FIG. 4 depicts a die attach location 134 (shown in broken lines)surrounding an opening 116 on the first surface 112 of the carriersubstrate 110. The adhesive elements 130 of the first embodiment may bearranged to provide a plurality of discrete point pads, wherein thepoint pads may be arranged proximate each inside corner of the dieattach location 134. As depicted, additional point pads may beselectively placed, such as being positioned proximately inside the dieattach location 134 periphery and midway between the point padsproximate the inside corners, or any other suitable placement that maybe desired or required. The discrete point pads may be selectivelypositioned in a symmetrical or asymmetrical arrangement. At least three,and preferably four, discrete point pads should be used for stability.

FIG. 5 illustrates a die attach site 234 (shown in broken lines)surrounding an opening 216 on the first surface 212 of a carriersubstrate 210 with an arrangement of adhesive elements 230, according toa first variant of the first embodiment. The adhesive elements 230 ofthe first variant may be arranged to provide a plurality of discreteelongated pads laterally adjacent to the opening 216 and arranged to runlongitudinally parallel with the opening 216. As depicted, eachelongated pad may extend substantially the length of the die attach site234. In the alternative, the elongated pads may be broken into multiplepads extending along the length of the die attach site periphery, or anyother suitable placement that may be required.

FIG. 6 illustrates a die attach site 334 (shown in broken lines)surrounding an opening 316 on the first surface 312 of a carriersubstrate 310 with adhesive elements 330 thereon, according to a secondvariant of the first embodiment. The adhesive elements 330 of the secondvariant may be arranged to provide a plurality of discrete elongatedpads laterally adjacent to the opening 316 and arranged to extendtransverse thereto. As illustrated, the second variant may include threepads on each side of the opening 316. Alternatively, more or fewer padsmay be utilized on each side of the opening 316.

FIG. 7 illustrates a die attach site 434 (shown in broken lines)surrounding an opening 416 on the first surface 412 of the carriersubstrate 410 with adhesive elements 430 thereon, according to a thirdvariant of the first embodiment. The adhesive elements 430 of the thirdvariant may be arranged to provide one or more discrete pads positionedcentrally on each longitudinal side of the opening 416. As depicted, thethird variant may include a single pad positioned on each longitudinalside of the opening 416.

FIGS. 8-10 illustrate a method of packaging a semiconductor assembly 500according to a second embodiment of the present invention. Turning firstto FIG. 8, there is depicted a semiconductor die 520 attached to acarrier substrate 510. Semiconductor die 520 includes an active surface522 and a back surface 524, of which the back surface 524 is attached tocarrier substrate 510 with a plurality of adhesive elements 530providing a gap or standoff 532 between the semiconductor die 520 andthe carrier substrate 510. The carrier substrate 510 includes a firstsurface 512 with conductive pads or terminals 518 thereon and a secondsurface 514. With the active surface 522 of the semiconductor die 520exposed upward, wire bonds 528 may be formed to extend from bond pads526 thereon to the conductive pads or terminals 518 on the substrate510.

The adhesive elements 530 utilized in the second embodiment may bearranged in any manner so that the arrangement of adhesive elements 530provides a gap or standoff 532 between the semiconductor die 520 and thecarrier substrate 510. Similar to the adhesive element arrangementsdepicted in FIGS. 4-7, such adhesive element arrangements may also beutilized for the second embodiment as long as the arrangement provides agap or standoff 532 sufficient to facilitate introduction of adielectric filler material 540. As before, the adhesive elements 530 maybe any known adhesive material, such as a decal or adhesive-coated tape,epoxy drops or segments or preformed adhesive segments, that provides asufficient initial attachment between semiconductor die 520 and carriersubstrate 510. The adhesive element 530 may also comprise metallicelements, such as solder bumps or the like.

FIG. 9 illustrates filling the gap or standoff 532 with dielectricfiller material 540 from dispenser head 542 to provide a secure,permanent, substantially inflexible bond between the semiconductor die520 and the carrier substrate 510. The dielectric filler material 540also facilitates stabilization of at least a portion of the wire bonds528 proximate the conductive pads 518 on the first surface 512 of thecarrier substrate 510. Such stiffening may prevent wire sweep betweenadjacent wire bonds 528 during encapsulation of the semiconductor die520. Dielectric filler material may be alternatively, or additionally,applied over bond pads 526 on active surface 522. FIG. 10 illustratesthe semiconductor assembly 500 with an encapsulation material 550 moldedover at least the active surface 522 of the semiconductor die 520 or, asshown, over the entire semiconductor die 520 and surrounding area ofcarrier substrate 510.

As with the embodiment of FIGS. 1-3, semiconductor assembly 500 may beconfigured for flip-chip attachment to higher level packaging,configured as a vertical surface mount package (VSMP) using one or morerows of contacts along an edge of carrier substrate 510, or otherwise aswell known in the art.

As illustrated in block diagram form in FIG. 11, a semiconductorassembly 100, 500 of the present invention may be mounted to a circuitboard 610 in an electronic system 600, such as a computer system. In theelectronic system 600, the circuit board 610 may be connected to aprocessor device 620 which communicates with an input device 630 and anoutput device 640. The input device 630 may comprise a keyboard, mouse,joystick or any other type of electronic input device. The output device640 may comprise a monitor, printer or storage device, such as a diskdrive, or any other type of output device. The processor device 620 maybe, but is not limited to, a microprocessor or a circuit card includinghardware for processing instructions for the electronic system 600.Additional structure for the electronic system 600 is readily apparentto those of ordinary skill in the art.

Thus, it will be appreciated that the present invention provides a lesscostly, but structurally superior semiconductor assembly and packagethrough reduction or elimination of the use of adhesive-coated tape.Moisture problems are substantially eliminated and a robust,substantially rigid package is formed, reducing or eliminating stressdefects. Further, wire sweep problems are also substantially eliminated,increasing yield.

In addition, when molding a dielectric encapsulant material by transfermolding onto a board on chip assembly (such as that of FIG. 1), it ishighly desirable to introduce the molding compound forming thedielectric encapsulant material into the mold cavity containing thesemiconductor die attached to the carrier substrate to flow around thebottom (backside) of the semiconductor die first and then to finish atthe top (wire bond side). If the molding compound enters the opening orslot first, the pressure created in the mold cavity will cause themolding compound to bleed out of the mold cavity. By use of the presentinvention and introducing a dielectric filler material between thesemiconductor die and carrier substrate and into the slot prior totransfer molding, the front of the slot is effectively sealed and bleedduring the molding process is prevented.

Further, the present invention affords enhanced flexibility inassembling the semiconductor die to a carrier substrate. Without thepresent invention, there must be a certain amount or degree of overlapof the periphery of the semiconductor die over the carrier substratebeyond the opening or slot to prevent bleed. Unfortunately, and contraryto the overlap requirement, there also must be a certain amount ofclearance between an end of the slot and the first active bond pad ofthe semiconductor die at the end of a row of bond pads or thesemiconductor die cannot be wire bonded. The present invention, byenabling the filling of the slot with a dielectric filler material priorto transfer molding, enables one to center the semiconductor die withrespect to the slot, which effectively makes more die area available topopulate with active bond pads, enabling higher I/O counts and enhancingdesign flexibility.

While the present invention has been disclosed in terms of a certainpreferred embodiments and alternatives thereof, those of ordinary skillin the art will recognize and appreciate that the invention is not solimited. Additions, deletions and modifications to the disclosedembodiments may be effected without departing from the scope of theinvention as claimed herein. Similarly, features from one embodiment maybe combined with those of another while remaining within the scope ofthe invention.

1. A semiconductor assembly comprising: a carrier substrate; asemiconductor substrate adjacent the carrier substrate; at least oneadhesive element disposed in a standoff volume between the carriersubstrate and an opposing surface of the semiconductor substrate; and avolume of dielectric filler material disposed around the at least oneadhesive element in the standoff volume and bonding the semiconductorsubstrate to the carrier substrate, the dielectric filler materialfilling a majority of the standoff volume.
 2. The semiconductor assemblyof claim 1, further comprising at least one conductive element extendingbetween a first conductive pad on the semiconductor substrate and asecond conductive pad on the carrier substrate.
 3. The semiconductorassembly of claim 2, wherein the at least one conductive elementcomprises at least one wire having a first end bonded to the firstconductive pad on the semiconductor substrate and a second end bonded tothe second conductive pad on the carrier substrate.
 4. The semiconductorassembly of claim 3, wherein the carrier substrate comprises a firstsurface, a second surface, and an opening extending through the carriersubstrate between the first surface and the second surface, the at leastone conductive element extending through the opening of the carriersubstrate.
 5. The semiconductor assembly of claim 2, wherein thedielectric filler material surrounds at least a first portion of the atleast one conductive element.
 6. The semiconductor assembly of claim 5,further comprising a volume of dielectric encapsulation materialextending over at least a second portion of the at least one conductiveelement.
 7. The semiconductor assembly of claim 1, wherein the at leastone adhesive element comprises at least one non-conductive adhesiveelement.
 8. The semiconductor assembly of claim 7, wherein the at leastone adhesive element comprises a plurality of non-conductive adhesiveelements disposed in a substantially symmetrical adhesive elementarrangement.
 10. The semiconductor assembly of claim 8, wherein theplurality of non-conductive adhesive elements comprises a plurality ofmutually separate and discrete elongated pads.
 11. The semiconductorassembly of claim 1, wherein the semiconductor substrate is attached tothe carrier substrate primarily by the volume of dielectric fillermaterial.
 12. The semiconductor assembly of claim 1, wherein the atleast one adhesive element comprises at least one of a decal, a tapesegment, and a volume of adhesive.
 13. A semiconductor assemblycomprising: a carrier substrate; a semiconductor substrate adjacent thecarrier substrate; at least one adhesive element disposed in a standoffvolume between the carrier substrate and an opposing surface of thesemiconductor substrate; a first non-conductive material disposed aroundthe at least one adhesive element in the standoff volume and bonding thesemiconductor substrate to the carrier substrate, the firstnon-conductive material filling a majority of the standoff volume; andat least one conductive element comprising: a first end bonded to afirst conductive pad on the semiconductor substrate and surrounded bythe first non-conductive material; and a second end bonded to a secondconductive pad on the carrier substrate and surrounded by a secondnon-conductive material.
 14. The semiconductor assembly of claim 13,wherein the first non-conductive material comprises a dielectric fillermaterial and the second non-conductive material comprises an encapsulantmaterial.
 15. The semiconductor assembly of claim 13, wherein thesemiconductor substrate is attached to the carrier substrate primarilyby the first non-conductive material.
 16. The semiconductor assembly ofclaim 13, wherein the at least one conductive element comprises at leastone bond wire.
 17. The semiconductor assembly of claim 16, wherein thecarrier substrate comprises a first surface, a second surface, and anopening extending through the carrier substrate between the firstsurface and the second surface, the at least one bond wire extendingthrough the opening of the carrier substrate.
 18. The semiconductorassembly of claim 13, wherein the at least one adhesive elementcomprises at least one non-conductive adhesive element.
 19. Thesemiconductor assembly of claim 18, wherein the at least one adhesiveelement comprises a plurality of non-conductive adhesive elementsdisposed in a substantially symmetrical adhesive element arrangement.20. The semiconductor assembly of claim 19, wherein the plurality ofnon-conductive adhesive elements comprises a plurality of mutuallyseparate and discrete elongated pads.
 21. A method of forming asemiconductor assembly, comprising: attaching a semiconductor substrateto a carrier substrate with at least one adhesive element providing asubstantially open volume between the carrier substrate and thesemiconductor substrate; establishing an electrical connection between afirst conductive pad on the semiconductor substrate and a secondconductive pad on the carrier substrate; introducing an uncureddielectric material into the substantially open volume and around the atleast one adhesive element; and curing the dielectric material to form adielectric structure primarily bonding the semiconductor substrate tothe carrier substrate.
 22. The method of claim 21, wherein attaching asemiconductor substrate to a carrier substrate comprises aligning afirst conductive pad on the semiconductor substrate with an openingextending through the carrier substrate between a first surface of thecarrier substrate and a second surface of the carrier substrate.
 23. Themethod of claim 22, wherein establishing electric connection comprisesattaching a first end of a bond wire to the first conductive pad on thesemiconductor substrate and attaching a second end of a bond wire to asecond conductive pad on the carrier substrate, the bond wire extendingthrough the opening extending through the carrier substrate.
 24. Themethod of claim 21, wherein establishing an electrical connectioncomprises: bonding a first end of a conductive element to a firstconductive pad on the semiconductor substrate; and bonding a second endof a conductive element to a second conductive pad on the carriersubstrate.
 25. The method of claim 24, further comprising surroundingthe first end of the conductive element with the uncured dielectricfiller material.
 26. The method of claim 25, further comprisingsurrounding the second end of the conductive element with anencapsulation material.
 27. The method of claim 21, wherein attaching asemiconductor substrate to a carrier substrate comprises attaching asemiconductor substrate to a carrier substrate with at least onenon-conductive adhesive element.
 28. The method of claim 21, whereinattaching a semiconductor substrate to a carrier substrate comprisesattaching a semiconductor substrate to a carrier substrate with aplurality of mutually separate and discrete elongated pads.
 29. Themethod of claim 21, wherein attaching a semiconductor substrate to acarrier substrate comprises attaching a semiconductor substrate with atleast one of a decal, a tape segment, and a volume of adhesive.
 30. Themethod of claim 21, wherein introducing an uncured dielectric materialinto the substantially open volume comprises substantially filling thesubstantially open volume with the uncured dielectric filler material.31. The method of claim 21, wherein attaching a semiconductor substrateto a carrier substrate comprises attaching a back side of asemiconductor substrate to the carrier substrate.
 32. A method offorming a semiconductor assembly, comprising: attaching a semiconductorsubstrate to a carrier substrate with at least one adhesive elementproviding a substantially open volume between the carrier substrate andthe semiconductor substrate; attaching a first end of at least oneconductive element to a first conductive pad on the semiconductorsubstrate and a second end of the at least one conductive element to asecond conductive pad on the carrier substrate; substantiallysurrounding at least the first end of the at least one conductiveelement with a first non-conductive material; and substantiallysurrounding at least the second end of the at least one conductiveelement with a second non-conductive material differing from the firstnon-conductive material.
 33. The method of claim 32, wherein the atleast one conductive element comprises at least one bond wire.
 34. Themethod of claim 33, wherein attaching a semiconductor substrate to acarrier substrate comprises